PLANO — Texas Republicans voted in a U.S. Senate primary runoff on May 28, 2024, between incumbent Sen. John Cornyn and Texas Attorney General Ken Paxton. The winner will face Democratic state Rep. James Talarico in the November 2024 general election.

Cornyn led the March 3, 2024, Republican primary but failed to secure a majority in a three-way race that also included U.S. Rep. Wesley Hunt. About 2 million of Texas' 18.7 million voters participated in that contest, with Paxton winning rural counties by about 5 percentage points.

President Donald Trump endorsed Paxton on May 19, 2024, after early voting began on May 18, despite an earlier promise to endorse immediately after the March primary. Trump wrote in a social media post: "Ken Paxton has gone through a lot, in many cases, very unfairly, but he is a Fighter, and knows how to win. Our Country needs Fighters, and also Loyalty to the Cause of Greatness." Trump also criticized Cornyn as "VERY disloyal" and said he "was not supportive of me when times were tough" and "was very late in backing me."

Paxton wrote on social media: "Every Paxton Patriot must get to the polls TOMORROW. Stand with President Trump and fight for Texas." In a Fox News interview, he said: "John Cornyn fought Trump on the border. And you can go back over about a decade and see that he was not for the border wall." He added: "John Cornyn fought the president's reelection. He fought him in 2024, said his time had passed, and he fought him in 2016. So this is not a pro-Trump guy."

Cornyn defended his record in a Fox News Digital interview. "President Trump has called me a friend and a good man, and we've worked with him closely for both terms of office," he said. In a separate statement, Cornyn said: "I know who gets to choose our senators, and it's the people of Texas."

Cornyn's campaign and allied groups spent approximately $90 million on advertising since 2023, mostly attacking Paxton. Between March 3 and May 28, pro-Cornyn groups outspent Paxton's campaign and allied super PACs $16.5 million to $5.9 million, according to ad-tracking firm AdImpact. Pro-Cornyn ads criticized the Texas Attorney General's office handling of a Waco sex abuse case. Senate Majority Leader John Thune and the National Republican Senatorial Committee backed Cornyn.

Paxton was acquitted in a 2023 impeachment trial in the Texas Senate after the Texas House voted to impeach him. His wife filed for divorce in 2023.

Early voting in the runoff saw 829,262 Republican ballots cast, down from 1,342,995 in March, and 347,790 Democratic ballots, down from 1,493,355. The early voting period was shorter than in March and did not include weekend days.